Some rotorcraft use a directional system based on directing airflow around and out of the tail boom in replacement of the tail rotor, in a configuration generally known as NOTAR® (NO TAil Rotor). Such directional systems require a relatively high volume air flow which is typically generated by a fan driven from the transmission of the main rotor. In flight conditions with lower directional flow requirements, the excess airflow may be exhausted back to the environment in a direction which is not prejudicial to the flight handling of the rotorcraft.
Aircraft engine assemblies generally include heat exchanger(s) to cool used cooling fluids. The cooling airflow circulated through such heat exchangers is typically taken from the environment of the engine assembly and exhausted back to the environment after circulation through the heat exchanger(s).